Field of the Disclosure
The present disclosure relates to a touch sensitive device and a display device including the touch sensitive device, and more particularly, to a touch sensitive device made of an EAP (Electro Active Polymer) having a low driving voltage and high transmissivity and a display device including the touch sensitive device.
Description of the Related Art
A touch panel, a device sensing touch input by a user such as a touch on the screen of a display device or a gesture, is widely used in large display devices such as display devices in public facilities and a smart TV, including portable display devices such as a smartphone and a tablet PC. Touch panels are classified into a resistive type, a capacitive type, an ultrasonic type, an infrared type and so on.
However, there are not only studies on sensing touch input by a user being performed, but also studies on haptic devices delivering touch sense feedback, which a user can feel with fingers or a stylus pen, as feedback of touch input by a user.
As one example, a haptic device may use an ERM (Eccentric Rotating Mass) with a display device. The ERM is a vibration motor that generates mechanical vibration using eccentric force that is generated when a motor is operated by attaching a mass to a portion of the rotor of the motor. However, ERMs are made of an opaque material, so they should not be disposed on the front surface, but on the rear surface of the display panel in a display device. Further, since ERMs generate vibration by a motor, no specific portion of a display device vibrates, rather the entire display device vibrates. Accordingly, in a display device with the ERM, a problem occurs as touch sense feedback cannot be delivered only to the portion touched by a user. Further, since ERMs generate mechanical vibration through a motor, the response speed is low, and thus, they are difficult to be used as a vibration source in haptic devices.
Further, as another example of a haptic device, there is a haptic device using a LRA (Linear Resonant Actuator) with a display device. LRAs deliver touch sense feedback through vibration of a spring and a stainless oscillator that is generated by reciprocation of a permanent magnet in a solenoid. However, similar to ERMs, LRAs are also made of an opaque material and vibrate an entire display device, so LRAs have the same problem as ERMs. Further, LRAs should use a resonance frequency, so the resonance frequency is fixed between 150 Hz to 200 Hz. Accordingly, haptic devices equipped with an LRA have difficulty in generating various vibrations.
Haptic devices equipped with a piezo ceramic actuator have been used to solve these problems. Piezo ceramic actuators have a high response speed of several micro seconds and a large range of vibration frequency, so they can achieve vibrations within all frequency ranges that people can actually feel. However, piezo ceramic actuators are formed in the shape of a ceramic plate, causing them to be easily broken by an external shock due to low durability against an external shock. Further, piezo ceramic actuators have a problem that they are opaque like ERMs and LRAs, and are difficult to be made thin. Also, piezo ceramic actuators vibrate an entire display device as they are disposed on the rear surface of the display device.